Synthesis and characterization of Pt nanoparticles with different morphologies in mesoporous silica SBA-15 for methanol oxidation reaction

Tiny Ni particles dispersed in platelet SBA-15 materials induce high efficiency for CO2 methanation

In this study, short-channel SBA-15 with a platelet morphology (p-SBA-15) is used to support Ni to effectively enhance catalytic activity and CH₄ selectivity during CO₂ hydrogenation. The use of p-SBA-15 as a support can result in smaller Ni particle sizes than Ni particles on typical SBA-15 supports because p-SBA-15 possesses a larger surface area and a greater ability to provide metal-support interactions. The Ni/p-SBA-15 materials with tiny Ni particles exhibit enhanced catalytic activity toward CO₂ hydrogenation and CH₄ formation during CO₂ hydrogenation compared to the same Ni loading on a SBA-15 support. The presence of metal-support interaction on the Ni/p-SBA-15 catalyst may increase the possibility of abundance of strongly adsorbing sites for CO and CO₂, thus resulting in high reaction rates for CO₂ and CO hydrogenation. The reaction kinetics, reaction pathway and active sites were studied and correlated to the high catalytic activity for CO₂ hydrogenation to form CH₄.

Confinement of Pt nanoparticles in cage-type mesoporous silica SBA-16 as efficient catalysts for toluene oxidation: the effect of carboxylic groups on the mesopore surface

In this work, 3D cage-type mesoporous SBA-16 materials functionalized with –COOH groups are used to support Pt metals and provide high catalytic activity for toluene oxidation.

Construction of Hierarchically Porous Nanoparticles@Metal-Organic Frameworks Composites by Inherent Defects for the Enhancement of Catalytic Efficiency

Nanoparticles@metal-organic frameworks (MOFs) composites have attracted considerable attention in recent years due to the prominent selective catalytic activity. However, it is highly desirable to develop a simple and universal way to settle the trade-off between the catalytic efficiency and selectivity. Herein, by employing the thermal instability of inherent defects, hierarchically porous Pt@UiO-66-NH₂ , Pt@UiO-66, Pt@ZIF-8, and Au@ZIF-8 are successfully constructed after annealing at an appropriate temperature, respectively. The generated mesopores in the MOFs can be located around the external nanoparticle to retain the MOF shell for catalytic selectivity. Finally, when tested in olefin hydrogenation, Pt@UiO-66-NH₂ shows significantly improved catalytic rate and enhanced dynamic selectivity.

Decomposition of Large Cu Crystals into Ultrasmall Particles Using Chemical Vapor Deposition and Their Application in Selective Propylene Oxidation

In this work, we report a novel application of chemical vapor deposition (CVD) in which the calcination and reduction of Cu(thd)₂ deposited onto 4.9 wt % Cu/SiO₂ induces significant decomposition of 28 nm crystalline Cu into ultrasmall ∼2 nm particles (5.1 wt % Cu/SiO₂). The Cu loading slightly increased, but the particle size dramatically decreased. The deposition of Cu(thd)₂ onto the Cu surface can initially affect the size reduction of the metallic Cu particles due to charge transfer between Cu(thd)₂ and the Cu surface. Thermal treatments, including calcination in air and reduction in H₂, can further influence the Cu particle decomposition. The mechanism of change in the Cu particle decomposition was investigated by a variety of experiments, such as X-ray diffraction and in situ X-ray absorption spectroscopy. CVD treatment of Cu/SiO₂ can create Cu-rich sites, which effectively enhance the conversion and acrolein yield in selective propylene oxidation. The intermediate associated with propylene oxidation on the Cu catalysts was also examined by IR spectroscopy.

High electrocatalytic performance inspired by crystalline/amorphous interface in PtPb nanoplate

Nanoscale PtPb catalysts with core-shell structure have been actively explored in recent years owing to their outstanding catalytic activity. We report on a new class of PtPb nanoplate (NP) catalyst with a novel structure realized by ion irradiation modification, which contains an interface formed by a crystalline phase and an amorphous phase simultaneously in an annular state. Significantly, the PtPb NP with the new structure shows superior catalytic activity towards the methanol oxidation reaction (MOR). The specific activity of PtPb NPs with the new structure reaches 4.32 mA cm-2 towards the MOR and the mass activity reaches 1.31 A mg-1, which is 1.9-fold and 1.4-fold greater than those for the original crystalline PtPb NPs, respectively. The outstanding catalytic activity could be attributed to the presence of the interface between a crystalline phase and an amorphous phase with a special electronic structure created by ion irradiation. Density functional theory calculations reveal that the novel interface activates the C-H and O-H bonds, leading to high electrocatalytic activity, and optimizes the adsorption of hydroxyl and intermediates on the surface to facilitate the oxidation reaction. The novel structure with an interface formed by a crystalline phase and an amorphous phase opens up a new approach to improve electrocatalytic activity.

Rare-earth element doping-promoted toluene low-temperature combustion over mesostructured CuMCeOx (M = Y, Eu, Ho, and Sm) catalysts: the indispensable role of in situ generated oxygen vacancies

The synergetic effect between Ho and the CuCeO_x framework creates abundant active oxygen vacancies and significantly enhances the toluene destruction activity.

ZnO@C (core@shell) microspheres derived from spent coffee grounds as applicable non-precious electrode material for DMFCs

Although numerous reports have introduced non precious electrocatalysts for methanol oxidation, most of those studies did not consider the corresponding high onset potential which restricts utilization in real fuel cells. In this study, an -90 mV [vs. Ag/AgCl] onset potential non-precious electrocatalyst is introduced as an applicable anode material for the direct methanol fuel cells. Moreover, the proposed material was prepared from a cheap and abundantly existing resource; the spent coffee grounds. Typically, the spent coffee grounds were facilely converted to core@shell (ZnO@C) microspheres through a two-step approach, involving chemical activation and a subsequent calcination at temperature of 700 °C. Activation of the carbon derived from the spent coffee grounds was performed with ZnCl₂ which acts as pore-forming agent as well as a precursor for the ZnO. The structure and morphology were characterized by (XRD), (SEM), and (TEM) analyses while the electrochemical characterizations was evaluated by cyclic voltammetry (CV) technique. Besides the comparatively very low onset potential, the introduced microspheres exhibited relatively high current density; 17 mA/cm². Overall, based on the advantages of the green source of carbon and the good electrocatalytic activity, the spent coffee grounds-derived carbon can be considered a promise anode material for the DMFCs.

Microbial synthesis of bimetallic PdPt nanoparticles for catalytic reduction of 4-nitrophenol

Bimetallic nanoparticles are generally believed to have improved catalytic activity and stability due to geometric and electronic changes. In this work, biogenic-Pd (bio-Pd), biogenic-Pt (bio-Pt), and biogenic-PdPt (bio-PdPt) nanoparticles were synthesized by Shewanella oneidensis MR-1 in the absence or presence of quinone. Compared with direct microbial reduction process, the addition of anthraquinone-2,6-disulfonate (AQDS) could promote the reduction efficiency of Pd(II) or/and Pt(IV) and result in decrease of particles size. All kinds of nanoparticles could catalyze 4-nitrophenol reduction by NaBH₄ and their catalytic activities took the following order: bio-PdPt (AQDS) ∼ bio-PdPt > bio-Pd (AQDS) > bio-Pd > bio-Pt (AQDS) ∼ bio-Pt. Moreover, the bio-PdPt (AQDS) nanoparticles could be reused for 6 cycles. We believe that this simple and efficient biosynthesis approach for synthesizing bimetallic bio-PdPt nanocatalysts is important for preparing active and stable catalysts.

Benzene hydrogenation over alumina-supported nickel nanoparticles prepared by polyol method

The reactivity of alumina-supported nickel catalysts can be improved by storing hydrogen in catalysts. This illustrates that a smooth correlation exists between the amount of stored hydrogen in catalysts and the catalytic activity.

Synthesis of sub-nanosized Pt particles on mesoporous SBA-15 material and its application to the CO oxidation reaction

In this work, we show that the size and shape of Pt nanoparticles in SBA-15 can be controlled through vacuum and air calcination. The vacuum-calcination/H2-reduction process is used to thermally treat a 0.2 wt% Pt(4+)/SBA-15 sample to obtain small 2D clusters and single atoms that can significantly increase Pt dispersion in SBA-15. Compared with thermal treatments involving air-calcination/H2-reduction, which result in ∼4.6 nm rod-like Pt particles, vacuum-calcination/H2-reduction can dramatically reduce the size of the Pt species to approximately 0.5-0.8 nm. The Pt particles undergoing air-calcination/H2-reduction have poor conversion efficiency because the fraction of terrace sites, the major sites for CO oxidation, on the rod-like Pt particles is small. In contrast, a large amount of low-coordinated Pt sites associated with 2D Pt species and single Pt atoms in SBA-15 is effectively generated through the vacuum-calcination/H2-reduction process, which may facilitate CO adsorption and induce strong reactivity toward CO oxidation. We investigated the effect of vacuum-calcination/H2-reduction on the formation of tiny 2D clusters and single atoms by characterizing the particles, elucidating the mechanism of formation, determining the active sites for CO oxidation and measuring the heat of CO adsorption.

Mercaptosilane-assisted synthesis of sub-nanosized Pt particles within hierarchically porous ZSM-5/SBA-15 materials and their enhanced hydrogenation properties

A novel catalyst that consists of sub-nanosized Pt particles within hierarchically porous ZSM-5/SBA-15 materials was synthesized. This catalyst exhibited high stability and a hierarchically porous structure of a micro-mesoporous composite and possessed a high density of active sites by confinement of sub-nanosized Pt particles within small-pore zeolites, showing high catalytic properties for the hydrogenation of 1,3-butadiene and cyclooctadiene at room temperature.

Dendritic Pt@Au nanowires as nanocarriers and signal enhancers for sensitive electrochemical detection of carcinoembryonic antigen

An electrochemical aptasensor for the sensitive and selective determination of carcinoembryonic antigen was constructed based on dendritic Pt@AuNWs as nanocarriers and signal enhancers.